Self-supporting, pleated, spirally wound filter

ABSTRACT

A coreless filter comprises a pleated, spirally wound loop of material disposed in a housing. The loop includes a layer of filter material, such as a membrane filter, interposed between two support layers.

RELATED APPLICATION

This application is a continuation-in-part of patent application Ser.No. 08/133,999, filed Oct. 12, 1993 now U.S. Pat. No. 5,403,482.

FIELD OF THE INVENTION

This invention relates generally to filters. More specifically, theinvention relates to a single pass filter device which is selfsupporting and coreless.

BACKGROUND OF THE INVENTION

Filtering processes are widely used to remove a variety of contaminantsfrom a gaseous or liquid fluid stream. In a filtering process, the fluidis passed, either singly or repeatedly, through a filter medium;therefore, filter throughput is effectively limited by the surface areaof the medium, and high capacity filters include large area bodies offilter medium. In order to minimize the size of filter assemblies, avariety of filter configurations have been developed. The choice ofconfiguration will depend upon the nature of the filter medium itself aswell as the process requirements of the filtration, for example, volumebeing filtered, pressure drop, the nature of the contaminants and soforth.

One particular type of filter configuration includes a spirally woundbody of filter medium disposed so that the fluid stream will either passaxially or radially therethrough. Another type of configurationcomprises a pleated medium. One specific configuration of pleated mediumcomprises a relatively planar medium, formed into a cylinder and pleatedlongitudinally. In some instances, the pleats are spirally wrapped aboutthe axis of the cylinder. Such spirally wrapped, pleated configurationsare occasionally referred to as semi-spirally wound filters. U.S. Pat.Nos. 3,042,571 and 2,1322,548 disclose various configurations ofpleated, and spirally wound filters.

One particularly important class of filters includes porous membranefilter elements. These membranes are typically fabricated from polymericmaterials and include pores having precisely controlled sizes rangingfrom macroporous through microporous to ultraporous. Such membranes aretypically fairly thin and fragile, and filters including porousmembranes usually incorporate a support element. U.S. Pat. No. 4,500,426discloses a number of configurations of filters including porousmembranes, and FIGS. 13-18 disclose a pleated, spirally wound membranefilter. As shown therein, the membrane is folded about a spacer andwound about a central core. The central core is necessary to providesupport and stability to the filter element so as to prevent damage tothe relatively fragile membrane. It is desirable to eliminate thecentral core for a number of reasons. The core limits the active area ofthe filter to some degree, and the use of a core increases the materialcost of the filter element as well as the time and labor required forits manufacture; however, prior art membrane filters have not hadsufficient structural integrity to permit their manufacture without acentral support core. The present invention provides a uniqueconfiguration of pleated, spirally wound filter which incorporates aporous membrane as the active filter element thereof. The filter of thepresent invention is a self-supporting, coreless structure. It is easyto fabricate and highly efficient in both its use of materials and itsoperation. These and other advantages of the present invention will bereadily apparent from the drawings, discussion and description whichfollow.

BRIEF DESCRIPTION OF THE INVENTION

There is disclosed herein a coreless filter. The filter includes agenerally cylindrical filter element, having an exterior surface, whichcomprises a first elongated strip of a first support material which hasits ends joined together to form a first support loop; a secondelongated strip of a second support material having its ends joinedtogether to form a second support loop concentric with the first supportloop; and, an elongated strip of filter material which has its endsjoined together to form a filter loop. The filter loop is concentricwith, and interposed between, the first and second support loops. Theloops comprising the filter element are configured into a pleated,spirally wound cylindrical body which includes a plurality of inwardpleats and a plurality of outward pleats in an alternating relationship.The inward pleats are directed toward a central axis of the filterelement and their apices are disposed in an abutting relationship so asto form a column having first and second open ends which defines acentral passageway therethrough. The pleats are wrapped about thecentral axis so that the apices of the outward pleats are tangentiallydisposed on an exterior surface of the cylindrical filter element. Thefilter further includes a housing which encloses the filter element, oneor both of the first and second open ends being sealed or bonded with anend seal or with an end cap, the end seal or end cap comprising a fluidflow conduit in open communication with the central passageway. Thehousing in one embodiment has a first fluid flow conduit incommunication with the central passageway and a second fluid flowconduit in communication with the exterior surface of the filter elementand in the other embodiment has both fluid flow conduits incommunication with the central passageway. In use, a fluid introducedinto one of the conduits passes through the support material and filtermaterial and exits through the other conduit.

The filter material includes a porous membrane which may be ahydrophilic membrane or a hydrophobic membrane and in one embodimentpreferably is a hydrophilic membrane which preferably is isotropic. Thepore size of the membrane may range from microporous to macroporous, andpreferably includes pores of up to 10 microns in size. The filtermaterial may comprise a single layer membrane or a multi-layeredstructure. The support material is a macroporous material and mayinclude woven and non-woven structures as well as extruded porousstructures. Typically the area of the filter medium is no more than1,000 square cm., and most preferably approximately 250 square cm.

The present invention also includes a method for the fabrication of thefilter wherein a cylindrical loop of material comprised of a filtermaterial sandwiched between layers of support material is pleated andspirally wound so as to provide the filter element which is subsequentlydisposed in a housing. The method, for the manufacture of a corelessfilter having a central axis and an exterior surface, includes the stepsof:

providing first and second elongated strips of support material;

interposing an elongated strip of filter material between said first andsaid second strips of support material;

joining the ends of said elongated strips so as to form a cylindricalloop;

forming a plurality of alternating inward and outward pleats in theloop, the inward pleats each having an apex directed toward the centralaxis of the loop; the outward pleats each having an apex directed awayfrom the center of said loop, these inward and outward pleats beingdisposed in alternating relationship;

wrapping the outward pleats about the central axis of the loop so as toform a cylindrical filter element having the exterior surface andfurther having first and second open ends in which the filter elementapex of each inwardly directed loop is disposed in abutting relationshipso as to form a column which defines a central passageway through thecylindrical element, and the apex of each outward loop is disposed uponthe exterior surface of the cylindrical filter element; and sealing orbonding one open end or both of the first and second open ends of thefilter element with an end seal or an end cap, each such end seal or endcap having a fluid flow conduit in communication with the centralpassageway of the filter element.

The invention also includes a method for the manufacture of a corelessfilter as described, comprising the step of disposing the filter elementin a filter housing, the filter housing including first and second fluidflow conduits in communication with the central passageway of the filterelement or including a first fluid conduit in communication with thecentral passageway of the filter element and a second fluid flow conduitin communication with the exterior surface of the cylindrical element.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an exploded, perspective view of one embodiment of a filterstructured in accord with the present invention;

FIG. 2 is an exploded, perspective view of two strips of supportmaterial and an interposed body of filter material;

FIG. 3 is a perspective view of a loop of material at one stage in themanufacture of the filter element of the present invention; the loopbeing partly cut away to show the individual support material strips andfilter material strip;

FIG. 4 is a top plan view of a pleated loop of material at another stagein its processing;

FIG. 5 is a top plan view of a pleated, spirally wrapped loop ofmaterial at a further stage in its processing;

FIG. 6 is a perspective view of an extruded spacer material;

FIG. 7 is a cross-sectional view of a multi-layered body of filtermaterial;

FIG. 8 is a perspective view of another embodiment of a filter having anopen housing and end caps, structured in accord with the presentinvention;

FIG. 9 is a similar view of an open housing filter with the end cappartly cut away to show the disposition of apices of pleats tightlypacked so as to form a rigid open column defining a central passageway;

FIG. 10 is an exploded, perspective view of a filter having an openhousing and end caps structured in accord with the invention; and

FIG. 11 is a side view of a filter housing, with the side wall of thehousing being partly cut away to show an inner, open housing filteraccording to a preferred embodiment of the invention.

DETAILED DESCRIPTION OF THE INVENTION

Referring now to FIG. 1, there is shown an exploded, perspective view ofone embodiment of a filter 10 structured in accord with the presentinvention. The filter includes a generally cylindrical filter element12, as will be described in greater detail hereinbelow, together with ahousing which, in this embodiment is comprised of an end cap 14a and amain housing 14b open at one end and closed at the other end. The endcap 14a includes a fluid conduit 16 which passes therethrough; and themain housing 14b includes another or second conduit 18 in communicationwith the interior thereof.

When the filter 10 is assembled, the filter element 12 is spirallywrapped, so that it becomes rigid and forms a central passageway 20, isfitted into the main housing 14b in a tight spiral, and sealed thereinby the end cap 14a. Sealing may be accomplished by the use of anadhesive, by thermal bonding, or by any other method which will affixthe end cap 14a to the main body 14b of the housing, preferably the endface 14c of the cap to the end of the main body. The end cap 14a issealed to the filter element 12 so that the conduit 16 associatedtherewith communicates directly with the central passageway 20 of thefilter element 12. In order to assure a tight seal, it is generallypreferable that the face 14c of the end cap 14a which contacts thefilter element 12 is scaled thereto with a fluid-tight material so thatany fluid passing through the conduit 16 and into the central passageway20 will be constrained to travel through the element 12 to the exteriorthereof. The conduit 18 is in fluid communication with the interior ofthe main housing 14b; and accordingly, is also in fluid communicationwith the exterior surface 22 of the filter element. It will thus be seenthat a fluid introduced into one of the conduits 16 or 18 will beconstrained to travel through the filter element 12 and to exit throughthe other conduit 18 or 16.

The filter element of the present invention is novel insofar as it is aself-supporting structure having sufficient rigidity and integrity thatthe use of a core element, as was standard in the prior art, is notneeded. The filter element basically comprises a pleated, spirally woundmember fabricated from a layered structure which includes a body offilter material 24 interposed between two supporting layers.

FIGS. 2-5 depict various stages in the fabrication of the filter elementof the present invention. Referring now to FIG. 2, there is shown a bodyof filter material 24 sandwiched between a layer of a first supportmaterial 26 and, a layer of a second support material 28. In thisfigure, the layers 24-28 are shown in a spaced-apart, explodedrelationship; although, it is to be understood that in the practice ofthe present invention the layers are in a generally superposed,contacting relationship. The layers of support material 26 and 28 areopen in cross section, that is to say they are sufficiently porous topermit the ready passage of fluid therethrough, it being understood thatin the context of the present invention, fluid is meant to define anyliquid or gaseous medium, which may or may not include solid particlesentrained therein. The support material should be resistant todegradation by any fluids which the filter will encounter. The materialshould have sufficient mechanical strength to permit processing and toprovide a stable structure to the filter element. The support materialshould be non-compressible, or only slightly compressible over theanticipated pressure range in which the filter operates. A variety ofmaterials meet the foregoing criteria. In general, the support materialis preferably a woven or non-woven fabric. Organic polymers comprise oneparticularly preferred support material since they are relatively rigidand inert and may be fabricated into a variety of structures having opencross sections. Polypropylene, nylon, polyester, polyamide andfluoropolymers, and the like, for example, are some materials havingparticular advantage in the practice of the invention. In someinstances, porous paper may be employed as a support material. Anotherpreferred support material comprises a molded or extruded screen or meshof polymeric material and FIG. 6 depicts a body of support material 30comprised of a sheet of polymer 32 having a plurality of openingsdefined therein.

The filter material 24, which is disposed between, and supported by thelayers of support material 26 and 28, may comprise any one of a numberof relatively thin, flexible media, including cloth, filter paper andthe like; although, it has been found that the configuration of thepresent invention has particular advantage in connection with porousmembrane filters. As mentioned hereinabove, these materials aretypically thin and relatively fragile and the dual supported structureof the present invention assures a high degree of integrity to thefilter material 24. One particularly preferred group of membranescomprises hydrophilic membranes; and, such membranes may be fabricatedfrom a variety of polymers including polyethersulfone, polysulfone,fluoropolymers such as polytetrafluoroethylene, polypropylene, celluloseacetate and the like. As is known in the art, porous membranes may beprepared from these materials by techniques which involve precipitatinglayers from a solution in a manner which provides a controlled porosityto the resultant product. In general, the pore size of membranes of thistype may be varied over a range extending from microporous tomacroporous. The present invention has found particular utility for thepreparation of filters from material having a porosity of up to 10microns. A typical porosity range of filters of the present invention isapproximately 0.1-10 microns, although it is to be understood that thepresent invention presents no impediment to the use of various membraneshaving larger or smaller pore sizes.

While FIG. 2 illustrates the filter material 24 as being a single layer,it is to be understood that, in some embodiments, the filter materialmay comprise a multi-layered structure. Referring now to FIG. 7, thereis shown a body of filter material 24 which is configured as threeseparate filter layers 34, 36 and 38, it being understood that a largeror smaller number of layers may be similarly employed. In particularembodiments, all the layers of the multi-layered filter material maycomprise porous filter media. For example, in some embodiments it may bedesirable to provide a series of stacked layers of sequentiallylayer-for-layer decreasing pore sizes. For example, in the structureshown in FIG. 7, the topmost layer 38 may be a relatively wide poredmaterial, the layer 36 a narrower pored material, and the layer 34 afine pored material. In this manner, the large pored layers act as aprefilter which limits clogging of the final pored layers by largeparticles. In some instances, the porosity of all the layers may be thesame. In other instances, some of the layers of the multi-layeredstructure may be a porous membrane material whereas others may comprisefurther supporting, separating or protective layers. For example, in theillustration of FIG. 7, layers 38 and 34 may comprise a membranematerial and layer 36 a spacer or support layer. Obviously, the reversestructure is also contemplated within the scope of the presentinvention. Therefore, it will be appreciated that in the context of thisdisclosure, the filter material may include a variety of structuralconfigurations.

As illustrated in FIG. 2, the layers of support material 26 and 28, andthe layer of filter material 24 are shown as generally elongated stripsof material, and it will be noted that they are generally coextensive.In a subsequent step, the layers are formed into a loop, as shown at 40in FIG. 3. The loop 40 of FIG. 3 comprises a loop of the first supportmaterial, a loop of the second support material and a loop of the filtermaterial disposed in a generally superposed and concentric relationship.The loop 40 may be formed by joining the ends of the strips of supportand filter material together, either separately, or in a concertedprocess. It is most preferred, for general economy of production, toprovide a strip consisting of the three stacked layers and to simplyjoin all the ends together along a seam 42 in a single step. The ends ofthe strips may be .joined by the use of adhesives, by mechanicalprocesses such as stitching, stapling and the like. In those instanceswhere the various layers are thermoplastic layers they may beadvantageously joined by a thermal welding process. In some otherinstances, solvent bonding may be employed.

In a subsequent processing step as illustrated in FIG. 4, the loop 40 isformed into a pleated structure. As illustrated, the loop includes aplurality of inward pleats, as for example pleats 44, 46 and 48. Theinward pleats are directed toward a central axis 50 of the loop 40. Thepleated loop also includes a series of outward pleats, 52, 54, 56 and 58for example, which are in an alternating relationship with the inwardpleats. As will be noted, alternating inward pleats and outward pleatsshare common sidewalls; hence, it is to be understood that in thecontext of this disclosure, an outward pleat is a pleat having a pair ofsidewalls meeting at an apex or crest directed away from the centralaxis of the loop, and an inward pleat is defined by a pair of sidewallsmeeting at an apex or crest which is directed toward the central axis.

The pleating process may be advantageously carried out quite simply by amechanical jig. For example, a jig may be configured to have a series ofmovable pins corresponding in number to the desired number of inward andoutward pleats. These pins may be disposed about the loop in two groups,a first surrounding the outside of the loop and a second surrounding theinside of the loop. In order to make the pleats, the outer group of pinsis moved inward toward the central axis 50 and in so doing form theinward pleats. The group of pins on the inside of the loop aredisplaceable toward the central axis, but they are preferably springloaded to provide a resistance to inward motion. When the first group ofpins is moved inwardly, the second group also travels inward to somedegree, but to a lesser degree than the first group of pins, and in sodoing they form the outward pleats. Clearly, other mechanicalarrangements may be similarly implemented.

It is to be appreciated that the present invention does not require thatthe loop be formed prior to the pleating. In some instances, it may beexpedient to pleat a strip of material and subsequently assemble it intoa loop to form a structure generally similar to that of FIG. 4. Suchembodiments are also within the scope of this disclosure and theinvention.

In the next processing step, as illustrated in FIG. 5, the pleated loop40 is spirally wound. The winding process is carried out by wrapping thepleats, about the central axis 50. The wrapping process compresses theloop so as to provide a cylindrical filter element, for example, asillustrated at reference numeral 12 in FIG. 1 and further shown as moretightly wrapped for greater rigidity in FIG. 9 so that a core forstructural strength is unnecessary. The wrapping process brings theinward pleats into a configuration wherein the apices or crests thereof,for example, 44a, 46a and 48a, are disposed in an abutting relationshipabout the central axis 50 so as to form a column which &fines thecentral passageway 20 of the filter element. In the final configuration,the outward pleats are disposed with their apices, for example 52a, 54a,56a, 58a, generally tangent to the surface of the cylindrical filterelement.

It will be understood from reference to FIG. 5, that a fluid introducedinto the central passageway 20 of the filter element will pass in agenerally perpendicular direction through the various layers of the loop40. Similarly, a fluid introduced exteriorly of the filter medium willpass in the reverse direction through to the central passageway 20.Thus, it will be appreciated that the structure of the present inventionprovides a single pass filter wherein flow is generally perpendicular tothe filter medium. The configuration of the present invention provides alarge area of filter material packaged in a relatively small volume.Most importantly, the pleated structure is quite strong because eachpleat cross section becomes a significant mechanical column resistant toboth compressive and torsional distortion. Additionally, each pleatclosely abuts adjacent pleats in such a way that the entire pleat packformation becomes a strong and rigid structure capable of withstandingtypical mechanical pressures associated with dead-end filtration withoutsuffering significant distortion.

The lack of the central core greatly simplifies the manufacture of thefilter since the steps of attaching a core and affixing the core to thefluid inlets need not be implemented. Also, the coreless structureprovides less impediment to fluid flow and hence smaller pressure dropsacross the filter. The filter structure of the present invention may bemanufactured in a variety of configurations, although it is mostpreferred that it be employed with filters having an active filtermedium area of no more than 1,000 square cm, said term being defined asthe surface area of the filter medium available for fluid flowtherethrough. One particularly preferred filter includes an active areaof approximately 250 square cm, and it has been found that this filtercan readily withstand a pressure of 40 psi without distortion.

To some degree the strength of the filter element will depend upon theaspect ratio of the filter element, such term being understood to meanthe ratio of the height to the diameter of the cylindrical element. Afilter element having a very high aspect ratio, i.e., a very tall narrowcylinder, will not be very resistant to loading either in a directionperpendicular to the axis of the cylinder or in a radial direction;hence, a filter of this type would not be very durable and could notsustain a large pressure drop thereacross. A filter element having avery low aspect ratio, i.e., a very short and wide filter element, wouldexhibit very high strength in both directions, but it would be difficultto fabricate and would consume relatively large amounts of material. Itis generally preferred that the filter medium have an aspect ratio inthe range of 0.25 to 5; although it is to be understood that forrelatively large area filters, i.e., filters with an active medium areagreater than 500 square cm., greater aspect ratios may be employed whileretaining sufficient strength.

While FIGS. 1 and 11 illustrate particular embodiments of filterswherein the filter medium is completely enclosed in a housing, it is tobe understood that other configurations are also within the scope of thepresent invention. For example, FIGS. 8, 9 and 10 depict a filter 60which includes an open housing structure. The filter 60 of FIG. 8includes a filter element 12 as previously described. Affixed bysuitable means such as adhesive to one end of the filter element 12 isthe face 14c of an end cap 14a generally similar to that of FIG. 1. Theend cap 14a includes a conduit 16 disposed to communicate with thecentral passageway (not shown) of the element 12. The remainder of thehousing comprises a top cap 62 disposed at its corresponding inward faceto seal the other end of the cylindrical filter element 12. In the FIG.9 embodiment, the remainder of the housing is cut away so as to exposethe outer perimeter of the element 12. In this embodiment, the cut-awayportion of the housing comprises the second conduit. This filter is ofparticular advantage in applications wherein the entire filter isimmersed in the fluid to be filtered. For example, filter 60 of FIGS. 8and 9 may be used to provide filtered air for a particular applicationby disposing the filter in the ambient atmosphere and drawing purifiedair out through the conduit 16. Similarly, the filter may be immersed ina liquid and filtered liquid drawn from the conduit 16.

As shown in FIG. 9, the open housing filter as assembled has a tightlywrapped spirally wound cylindrical structure that is rigidly sealedagainst radial displacement by end caps 14a, 62. One cap 14a comprises afluid conduit 16 that is in open communication with the centralpassageway 20. The outer perimeter purposely lacks a housing side wallso that it serves as an entry conduit for radial fluid flow through thefilter 12 into the central passageway for exit passage in turn throughthe conduit 16 of the end cap 14a; it also serves as an exit conduit forreverse radial fluid flow via conduit 16 used as an entry conduit.

As shown in FIG. 10, the filter element of the open housing filter 12 asassembled also has a tightly wrapped spirally wound cylindricalstructure and is rigidly sealed against radial displacement by end caps14a, 14a. The end caps 14a, 14a comprise fluid conduits 16,16 in opencommunication with the central passageway 20, but in assembly, the openend of one conduit is blocked by a fluid-tight end cap 62a. The outerperimeter 22 serves as an entry conduit for radial fluid flow throughthe filter 12 into the central passageway 20 for exit passage throughthe unblocked conduit; the perimeter also serves as an exit conduit forreverse radial fluid flow via conduit 16 used as an entry conduit. Afunctionally equivalent structure is one in which the end cap 14a on theblocked end is an imperforate end cap 62, and the conduit end cap 62a isomitted. The functional result is the same.

As shown in FIG. 11, the filter 10 in a preferred embodiment comprisesan end cap 14a for a generally cylindrical main housing 14b, the housingand end cap comprising fluid flow conduits 16,18 respectively. A filterelement 12 with end caps 62, 14 is located concentrically in the housingso that the central passageway 20 is in open communication with thefluid flow conduit 18, and the end cap 14 is rigidly sealed or formedthere in leakproof relation with the inner face of the housing end cap14a. The end cap 62 is imperforate and is rigidly sealed in leakproofrelation with the filter element 12. As shown, the filter element 12 iscompletely enclosed in the housing and is located so that the end cap 62and its parametrial surface 22 are spaced at a distance from theinterior surface of the main housing 14b thus allowing for free fluidflow in the open space within the housing. Thus, in operation, whenfluid is introduced to the fluid flow conduit 16 or 18 the fluid isconstrained to travel through the filter element 12 to the centralpassageway 20, and to exit from the housing through the other conduit 18or 16. In a preferred embodiment, the main housing 14b comprises a gasvent 14d for release of gas phase fluid.

Clearly, other configurations are also within the scope of the presentinvention. In view of the foregoing it will be understood that thedrawings, discussion and description herein is meant to illustrate, butnot limit, the scope of the present invention. It is the followingclaims, including all equivalents, which define the scope of theinvention.

We claim:
 1. A coreless filter comprising a cylindrical filter element including:a) a first elongated strip of a first support material having the ends thereof joined together to form a first support loop; b) a second elongated strip of a second support material having the ends thereof joined together to form a second support loop, said first and second support loops being disposed in a generally concentric relationship; c) an elongated strip of a filter material having the ends thereof joined together to form a filter loop, said filter loop being concentric with, and interposed between, said first and second support loops; d) said filter element being configured as a pleated, spirally wound, cylindrical body which includes a plurality of inward pleats and a plurality of outward pleats in an alternating relationship therewith, said inward pleats being directed toward a central axis of the cylindrical filter element and having apices which are disposed in an abutting relationship so as to form a column which defines a central passageway through the filter element having first and second open ends, said outward pleats being wrapped about said central axis so that apices of said outward pleats are tangentially disposed upon the exterior surface of said cylindrical filter element; c) One of said first and second open ends of said central passageway being scaled with an end cap having a fluid flow conduit in communication with said central passageway; said central passageway of said element does not include any supporting core member therein, the element having sufficient rigidity and integrity such that the use of a core member is not needed.
 2. A filter as in claim 1, wherein the other of said first and second open ends of said central passageway is sealed with a fluidtight end cap.
 3. A filter as in claim 1 comprising first and second fluid flow conduits and further comprising a filter housing enclosing said filter element, said first fluid flow conduit being in communication with the central passageway and said second fluid flow conduit being in communication with the exterior surface of the filter element that fluid introduced into one of the first and second fluid flow conduits passes through said first support material, said filter material and said second support material, and exits through the other of said first and second conduits.
 4. A filter as in claim 1, wherein said filter material comprises material selected from the group consisting of depth filter material, membrane filter material, layered filter material, and stacked filter material, and combinations of said filter material.
 5. A filter as in claim 4, wherein said membrane filter material is selected from the group consisting of hydrophilic membranes, hydrophobic membranes, and combinations thereof.
 6. A filter as in claim 4, wherein said membrane filter material has a pore size in the range of 0.1 to 10 microns.
 7. A filter as in claim 1, wherein the filter material comprises a plurality of layers of material disposed in superposed relationship.
 8. A filter as in claim 1, wherein said support material is selected from the group consisting of woven material, non-woven textile material, paper, non-woven mesh, and combinations thereof.
 9. A filter as in claim 3, configured as a closed housing structure comprising a main housing which completely encloses said filter element, said main housing defining said first and second fluid flow conduits. 